Autophagy and apoptosis have a role in the survival or death of stallion spermatozoa during conservation in refrigeration

ROS-induced oxidative stress is a major contributor to sperm cryoinjury

STUDY QUESTION

What is the mechanism behind cryoinjury in human sperm, particularly concerning the interplay between reactive oxygen species (ROS) and autophagy, and how does it subsequently affect sperm fate?

SUMMARY ANSWER

The freeze-thaw operation induces oxidative stress by generating abundant ROS, which impairs sperm motility and activates autophagy, ultimately guiding the sperm toward programmed cell death such as apoptosis and necrosis, as well as triggering premature capacitation.

WHAT IS KNOWN ALREADY

Both ROS-induced oxidative stress and autophagy are thought to exert an influence on the quality of frozen-thawed sperm.

STUDY DESIGN, SIZE, DURATION

Overall, 84 semen specimens were collected from young healthy fertile males, with careful quality evaluation. The specimens were split into three groups to investigate the ROS-induced cryoinjury: normal control without any treatment, sperm treated with 0.5 mM hydrogen peroxide (H2O2) for 1 h, and sperm thawed following cryopreservation. Samples from 48 individuals underwent computer-assisted human sperm analysis (CASA) to evaluate sperm quality in response to the treatments. Semen samples from three donors were analyzed for changes in the sperm proteome after H2O2 treatment, and another set of samples from three donors were analyzed for changes following the freeze-thaw process. The other 30 samples were used for fluorescence-staining and western blotting.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Sperm motility parameters, including progressive motility (PR %) and total motility (PR + NP %), were evaluated using the CASA system on a minimum of 200 spermatozoa. The proteomic profiles were determined with label-free mass spectrometry (MS/MS) and protein identification was performed via ion search against the NCBI human database. Subsequently, comprehensive bioinformatics was applied to detect significant proteomic changes and functional enrichment. Fluorescence-staining and western blot analyses were also conducted to confirm the proteomic changes on selected key proteins. The ROS level was measured using 2',7'-dichlorodihydrofluorescein diacetate labeling and the abundance of bioactive mitochondria was determined by evaluating the inner mitochondrial membrane potential (MMP) level. Molecular behaviors of sequestosome-1 (p62 or SQSTM1) and microtubule-associated proteins 1A/1B light chain 3 (LC3) were monitored to evaluate the state of apoptosis in human sperm. Fluorescent probes oxazole yellow (YO-PRO-1) and propidium iodide (PI) were utilized to monitor programmed cell death, namely apoptosis and necrosis. Additionally, gradient concentrations of antioxidant coenzyme Q10 (CoQ10) were introduced to suppress ROS impacts on sperm.

MAIN RESULTS AND THE ROLE OF CHANCE

The CASA analysis revealed a significant decrease in sperm motility for both the H2O2-treatment and freeze-thaw groups. Fluorescence staining showed that high ROS levels were produced in the treated sperm and the MMPs were largely reduced. The introduction of CoQ10 at concentrations of 20 and 30 μM resulted in a significant rescue of progressive motility (P < 0.05). The result suggested that excessive ROS could be the major cause of sperm motility impairment, likely by damaging mitochondrial energy generation. Autophagy was significantly activated in sperm when they were under oxidative stress, as evidenced by the upregulation of p62 and the increased conversion of LC3 as well as the upregulation of several autophagy-related proteins, such as charged multivesicular body protein 2a, mitochondrial import receptor subunit TOM22 homolog, and WD repeat domain phosphoinositide-interacting protein 2. Additionally, fluorescent staining indicated the occurrence of apoptosis and necrosis in both H2O2-treated sperm and post-thaw sperm. The cell death process can be suppressed when CoQ10 is introduced, which consolidates the view that ROS could be the major contributor to sperm cryoinjury. The freeze-thaw process could also initiate sperm premature capacitation, demonstrated by the prominent increase in tyrosine phosphorylated proteins, verified with anti-phosphotyrosine antibody and immunofluorescence assays. The upregulation of capacitation-related proteins, such as hyaluronidase 3 and Folate receptor alpha, supported this finding.

LARGE SCALE DATA

The data underlying this article are available in the article and its online supplementary material.

LIMITATIONS, REASONS FOR CAUTION

The semen samples were obtained exclusively from young, healthy, and fertile males with progressive motility exceeding 60%, which might overemphasize the positive effects while possibly neglecting the negative impacts of cryoinjury. Additionally, the H2O2 treatment conditions in this study may not precisely mimic the oxidative stress experienced by sperm after thawing from cryopreservation, potentially resulting in the omission of certain molecular alterations.

WIDER IMPLICATIONS OF THE FINDINGS

This study provides substantial proteomic data for a comprehensive and deeper understanding of the impact of cryopreservation on sperm quality. It will facilitate the design of optimal protocols for utilizing cryopreserved sperm to improve applications, such as ART, and help resolve various adverse situations caused by chemotherapy, radiotherapy, and surgery.

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported by grants from the Major Innovation Project of Research Institute of National Health Commission (#2022GJZD01-3) and the National Key R&D Program of China (#2018YFC1003600). All authors declare no competing interests.

TRIAL REGISTRATION NUMBER

N/A.

New strategies for germ cell cryopreservation: Cryoinjury modulation

Cryopreservation is an option for the preservation of pre- or post-pubertal female or male fertility. This technique not only is beneficial for human clinical applications, but also plays a crucial role in the breeding of livestock and endangered species. Unfortunately, frozen germ cells, including oocytes, sperm, embryos, and spermatogonial stem cells, are subject to cryoinjury. As a result, various cryoprotective agents and freezing techniques have been developed to mitigate this damage. Despite extensive research aimed at reducing apoptotic cell death during freezing, a low survival rate and impaired cell function are still observed after freeze-thawing. In recent decades, several cell death pathways other than apoptosis have been identified. However, the relationship between these pathways and cryoinjury is not yet fully understood, although necroptosis and autophagy appear to be linked to cryoinjury. Therefore, gaining a deeper understanding of the molecular mechanisms of cryoinjury could aid in the development of new strategies to enhance the effectiveness of the freezing of reproductive tissues. In this review, we focus on the pathways through which cryoinjury leads to cell death and propose novel approaches to enhance freezing efficacy based on signaling molecules.

Autophagy, a critical element in the aging male reproductive disorders and prostate cancer: a therapeutic point of view

Autophagy is a highly conserved, lysosome-dependent biological mechanism involved in the degradation and recycling of cellular components. There is growing evidence that autophagy is related to male reproductive biology, particularly spermatogenic and endocrinologic processes closely associated with male sexual and reproductive health. In recent decades, problems such as decreasing sperm count, erectile dysfunction, and infertility have worsened. In addition, reproductive health is closely related to overall health and comorbidity in aging men. In this review, we will outline the role of autophagy as a new player in aging male reproductive dysfunction and prostate cancer. We first provide an overview of the mechanisms of autophagy and its role in regulating male reproductive cells. We then focus on the link between autophagy and aging-related diseases. This is followed by a discussion of therapeutic strategies targeting autophagy before we end with limitations of current studies and suggestions for future developments in the field.

Protective Effect of Peptide Calcium Channel Blocker Omega-Hexatoxin-Hv1a on Epithelial Cell during Ischemia-Reperfusion Injury

Ischemia-reperfusion injury (IRI) is a common phenomenon that develops both from natural causes and during major operations. Many intracellular processes mediated by calcium ions are involved in the development of IRI. Currently, chemical calcium channel blockers are used but they have a number of limitations. In this article, we study the effect of the omega-hexatoxin-Hv1a peptide toxin, an alternative to chemical calcium channel blockers, on the mechanisms of IRI development in epithelial cell culture. The toxin was produced using solid phase peptide synthesis. IRI was caused by deprivation of glucose, serum and oxygen. The data obtained demonstrate that the omega-hexatoxin-Hv1a toxin in nanomolar concentrations is able to prevent the development of apoptosis and necrosis in epithelial cells by reducing the concentration of calcium, sodium and potassium ions, as well as by delaying rapid normalization of the pH level, affecting the mitochondrial potential and oxidative stress. This toxin can be used as an alternative to chemical calcium channel blockers for preventing tissue and organ IRI due to its low-dose requirement and high bioavailability.

Protective Effect of Docetaxel Against Autophagy-Related Genes in Vitrification of Mouse Metaphase II Oocytes

Background

Autophagy is a conservative mechanism for cell survival as the main response of cells to stress conditions. The present study aimed to assess the effect of docetaxel on the survival, fertilization, and expression of autophagy-related genes in vitrified oocytes.

Methods

The study was conducted in 2018 at the Stem Cells Technology Research Center, Shiraz University of Medical Sciences (Shiraz, Iran). Denuded oocytes were randomly selected and assigned to five groups, namely control (n=133), docetaxel (n=136), docetaxel+cryoprotectants (n=146), docetaxel+vitrification (n=138), and vitrification (n=145). The effect of vitrification on the expression of autophagy-related gene 5 (ATG5) and Beclin-1 was determined using a real-time polymerase chain reaction. Data were analyzed using SPSS software (version 26.0) and GraphPad Prism 9.

Results

Survival and fertilization rates in each experimental group were significantly reduced compared to the control group (P=0.001). After in vitro fertilization of oocytes, the 2-cell formation rate was significantly reduced in the docetaxel+vitrification and vitrification groups compared to the control and docetaxel groups (P=0.001 and P=0.001, respectively). Pre-incubation of oocytes with docetaxel reduced gene expression levels of Beclin-1 and ATG5 in the docetaxel+cryoprotectants and docetaxel+vitrification groups (P=0.001 and P=0.019, respectively). The expression level of these genes was also reduced in the docetaxel group compared to the control group (P=0.001).

Conclusion

Incubation of mouse metaphase II oocytes with docetaxel prior to vitrification reduced the expression of autophagy-related genes and increased survival and fertilization rates compared to untreated oocytes.

Role of Macroautophagy in Mammalian Male Reproductive Physiology

Physiologically, autophagy is an evolutionarily conserved and self-degradative process in cells. Autophagy carries out normal physiological roles throughout mammalian life. Accumulating evidence shows autophagy as a mechanism for cellular growth, development, differentiation, survival, and homeostasis. In male reproductive systems, normal spermatogenesis and steroidogenesis need a balance between degradation and energy supply to preserve cellular metabolic homeostasis. The main process of autophagy includes the formation and maturation of the phagophore, autophagosome, and autolysosome. Autophagy is controlled by a group of autophagy-related genes that form the core machinery of autophagy. Three types of autophagy mechanisms have been discovered in mammalian cells: macroautophagy, microautophagy, and chaperone-mediated autophagy. Autophagy is classified as non-selective or selective. Non-selective macroautophagy randomly engulfs the cytoplasmic components in autophagosomes that are degraded by lysosomal enzymes. While selective macroautophagy precisely identifies and degrades a specific element, current findings have shown the novel functional roles of autophagy in male reproduction. It has been recognized that dysfunction in the autophagy process can be associated with male infertility. Overall, this review provides an overview of the cellular and molecular basics of autophagy and summarizes the latest findings on the key role of autophagy in mammalian male reproductive physiology.

Peptide Sodium Channels Modulator Mu-Agatoxin-Aa1a Prevents Ischemia-Reperfusion Injury of Cells

Ischemia-reperfusion injury (IRI) is an irreversible functional and structural injury. Restoration of normal oxygen concentration exacerbates the emergence and development of deadly cells. One of the possible moments of reperfusion damage to cells is an increase in the intracellular concentration of sodium ions. In this article, we study the mu-agatoxin-Aa1a, a modulator of sodium channels, on the processes of IRI cells damage. The toxin was synthesized using an automatic peptide synthesizer. Hypoxia was induced by reducing the content of serum and oxygen in the CHO-K1 culture. The influence of the toxin on the level of apoptosis; intracellular concentration of sodium, calcium, and potassium ions; intracellular pH; totality of reactive oxygen species (ROS), nitric oxide (NO), and ATP; and changes in the mitochondrial potential were studied. The experiments performed show that mu-agatoxin-Aa1a effectively prevents IRI of cells. Toxin reduces the level of apoptosis and prevents a decrease in the intracellular concentration of sodium and calcium ions during IRI. Mu-agatoxin-Aa1a contributes to the maintenance of elevated intracellular pH, reduces the intracellular concentration of ROS, and prevents the decrease in intracellular NO concentration and mitochondrial potential under conditions of reoxygenation/reperfusion. An analysis of experimental data shows that the mu-agatoxin-Aa1a peptide has adaptogenic properties. In the future, this peptide can be used to prevent ischemia/reperfusion tissue damage different genesis.

The Autophagy Marker LC3 Is Processed during the Sperm Capacitation and the Acrosome Reaction and Translocates to the Acrosome Where It Colocalizes with the Acrosomal Membranes in Horse Spermatozoa

Despite its importance in somatic cells and during spermatogenesis, little is known about the role that autophagy may play in ejaculated spermatozoa. Our aim was to investigate whether the molecular components of autophagy, such as microtubule-associated protein 1 light chain 3 (LC3), are activated in stallion spermatozoa during the capacitation and acrosome reaction and if this activation could modulate these biological processes. To analyze the autophagy turnover, LC3I and LC3II proteins were assessed by western blotting, and the ratio between both proteins (LC3II/LC3I) was calculated. In somatic cells, this ratio indicates that autophagy has been activated and similar LC3 processing has been described in mammalian spermatozoa. The subcellular localization of autophagy-related proteins was assessed by immunofluorescence with specific antibodies that recognized Atg16, Beclin-1, and LC3. The colocalization of acrosomal membranes (PNA) and LC3 was studied by confocal microcopy, and the acrosome reacted cells were quantified by flow cytometry. The incubation of stallion sperm in capacitating conditions (BWW; 3 h) significantly increased LC3 processing. This increment was three to four times higher after the induction of the acrosome reaction in these cells. LC3 was mainly expressed in the head in mature ejaculated sperm showing a clear redistribution from the post-acrosomal region to the acrosome upon the incubation of sperm in capacitating conditions (BWW, 3 h). After the induction of the acrosome reaction, LC3 colocalized with the acrosome or the apical plasmalemma membranes in the head of the stallion spermatozoa. The inhibition or activation of autophagy-related pathways in the presence of autophagy activators (STF-62247) or inhibitors (E-64d, chloroquine) significantly increased LC3 processing and increased the percent of acrosome reacted cells, whereas 3-methyladenine almost completely inhibited LC3 processing and the acrosome reaction. In conclusion, we found that sperm capacitation and acrosome reaction could be regulated by autophagy components in sperm cells ex vivo by processes that might be independent of the intraluminal pH of the acrosome and dependent of LC3 lipidation. It can be speculated that, in stallion sperm, a form of noncanonical autophagy utilizes some components of autophagy machinery to facilitate the acrosome reaction.

Beneficial effects of trehalose and gentiobiose on human sperm cryopreservation

The protection of human sperm during cryopreservation is of great importance to infertility. Recent studies have shown that this area is still a long way from its ultimate aim of maintaining the maximum viability of sperm in cryopreservation. The present study used trehalose and gentiobiose to prepare the human sperm freezing medium during the freezing-thawing. The freezing medium of sperm was prepared with these sugars, and the sperm were then cryopreserved. The viable cells, sperm motility parameters, sperm morphology, membrane integrity, apoptosis, acrosome integrity, DNA fragmentation, mitochondrial membrane potential, reactive oxygen radicals, and malondialdehyde concentration was evaluated using standard protocols. A higher percentage of the total and progressive motility, rate of viable sperm, cell membrane integrity, DNA and acrosome integrity, and mitochondrial membrane potential were observed in the two frozen treatment groups compared to the frozen control. The cells had less abnormal morphology due to treatment with the new freezing medium than the frozen control. The higher malondialdehyde and DNA fragmentation were significantly observed in the two frozen treatment groups than in the frozen control. According to the results of this study, the use of trehalose and gentiobiose in the sperm freezing medium is a suitable strategy for sperm freezing to improve its motion and cellular parameters.

Differential gene expression analysis related to sperm storage in spermathecas of Amphioctopus fangsiao

Sperm storage in the female body is an important strategy in animal reproductive behavior. Amphioctopus fangsiao is an economically important cephalopod that has a sperm storage period of up to seven months. There are few studies concerning the mechanism of sperm storage in A. fangsiao. In this study, we performed transcriptome gene expression profiling of the oviductal glands at different phases (presence and absence of sperm storage). In total, 7943 differentially expressed genes (DEGs) comprising 4737 upregulated and 3206 downregulated genes were identified. GO and KEGG enrichment analyses were used to search for sperm storage-related genes. A protein interaction network was constructed to examine the interactions between genes. Nineteen genes associated with immunity, apoptosis, and autophagy were obtained and verified by qRT-PCR. This is the first comprehensive analysis of sperm storage-related genes in A. fangsiao. The results provide basic insights into the complex sperm storage mechanism of A. fangsiao.

Histology, ultrastructure, and differential gene expression in relation to seasonal sperm storage in the oviduct of the Chinese alligator, Alligator sinensis

Although oviductal sperm storage are essential steps in reproduction for female animals with internal fertilisation, no systematic study on the identification of genes involving sperm storage has been performed in crocodilian species. In the present research, the relationship between morphological variation related to sperm storage in the oviduct and gene expression patterns derived from RNA sequencing analyses between active period (AP), breeding period (BP), and hibernation period (HP) were investigated. The corresponding results indicated that sperm were observed not only in the ciliated cells within infundibulum and mucosal layer of uterus during BP, but also been detected in the spermatosperm storage tube (SST) in the anterior uterus at HP stage. The further transmission electron microscopy analysis indicated that the differences in the number and activity of the secretory cells likely to attributed to the seasonal variation of microenvironment related to the sperm storage. Based on the RNA-sequecing, 13147 DEGs related to the Peroxisome proliferator-activated receptors (PPARs) and FOXO signalling were identified, including these, the down-regulated ATG12 and BCL2L11 in the HP group may thus constitute an important point of convergence between autophagy and apoptosis involving the FOXO1 pathway. The genes involved in the PPARs pathway might modulate the immune response and thereby contribute to prolong the life span of stored spermatozoa in Alligator sinensis. The outcomes of this study provide fundamental insights into the mechanism of sperm storage in A. sinensis.

Autophagy modulation alleviates cryoinjury in murine spermatogonial stem cell cryopreservation

BACKGROUND

Cryopreservation can expand the usefulness of spermatogonial stem cells (SSCs) in various fields. However, previous investigations that have attempted to modulate cryoinjury-induced mechanisms to increase cryoprotective efficiency have mainly focused on apoptosis and necrosis.

OBJECTIVES

This study aimed to establish an effective molecular-based cryoprotectant for SSC cryopreservation via autophagy modulation.

MATERIALS AND METHODS

To determine the efficacy of autophagy modulation, we assessed the recovery rate and relative proliferation rate and performed western blotting for the determination of autophagy flux, immunocytochemistry and real-time quantitative polymerase chain reaction (RT-qPCR) for SSC characterization, and spermatogonial transplantation for in vivo SSC functional activity.

RESULTS

The results showed that a basal level of autophagy caused a higher relative proliferation rate (pifithrin-μ 0.01 μM, 184.2 ± 11.2%; 3-methyladenine 0.01 μM, 175.3 ± 10.3%; pifithrin-μ 0.01 μM + 3-methyladenine 0.01 μM, P3, 224.6 ± 22.3%) than the DMSO control (100 ± 6.2%). All treatment groups exhibited normal characteristics, suggesting that these modulators could be used as effective cryoprotectants without changing the properties of the undifferentiated germ cells. According to the results of the in vivo spermatogonial transplantation assay, the colonies per total number of cultured SSCs was significantly higher in the pifithrin-μ 0.01 μM (1596.7 ± 172.5 colonies), 3-methyladenine 0.01 μM (1522.1 ± 179.2 colonies), and P3 (1727.5 ± 196.5 colonies) treatment groups than in the DMSO control (842.8 ± 110.08 colonies), which was comparable to that of the fresh control (1882.1 ± 132.1 colonies).

DISCUSSION

A basal level of autophagy is more essential for resilience in frozen SSCs after thawing, rather than the excessive activation or inhibition of autophagy.

CONCLUSION

A basal level of autophagy plays a critical role in the pro-survival response of frozen SSCs after thawing; herein, a new approach by which SSC cryoprotective efficiency can be improved was identified.

Busulfan Suppresses Autophagy in Mouse Spermatogonial Progenitor Cells via mTOR of AKT and p53 Signaling Pathways

In testis, a rare undifferentiated germ cell population with the capacity to regenerate robustly and support spermatogenesis, is defined as spermatogonial progenitor cells (SPCs) population. As a widely used drug for tumor therapy or bone marrow transplantation, busulfan has a severe side effect on SPCs population and causes a consequent infertility. Recently, accumulating evidence revealed the protective role of autophagy in stem cell maintenance under exogenous stress. To better understand the role of autophagy in SPCs fates, we investigated the potential function of autophagy in SPCs under busulfan stress, and found that treatment of busulfan induced the formation of autophagic vesicles and autophagosomes in mouse SPCs. Subsequently, a connection of autophagy and SPCs maintenance and survival was demonstrated in a dose-dependent manner. Moreover, mTOR was identified as an essential factor for autophagy in SPCs with a complicated mechanism: (1) mTOR is phosphorylated by AKT to activate its target genes, p70s6 kinase, resulting in the inhibition of autophagy during short-term busulfan treatment. (2) mTOR mediates autophagy with p53 together, to regulate the fate of SPCs. Collectively, observations from this study indicate that moderate autophagy effectively protects SPCs from the stress of chemotherapy, which may provide an important hint for fertility protection in clinic.

Alteration in autophagy gene expression profile correlates with low sperm quality

AIMS

Low sperm quality, a crucial factor of male infertility, is becoming a public health issue all over the world. In male reproductive system, autophagy plays an important role in maintaining physiological functions. There exist conjectures that disordered autophagy autophagy might be related to low sperm quality. However, there is no evidence can confirm that. This study aims to investigate the association between autophagy-associated genes and low sperm quality.

METHODS

Sperm samples of low sperm quality cases and matched controls were included to select differential expressed genes (DE genes) by autophagy-related functional gene microarray analysis. Then, 104 cases and 250 controls were included to validate the expression of four important autophagy genes (CXCR4, ESR1, PTEN and LC3B). Based on the obtained DE gene, gene Ontology and pathway analyses were conducted.

RESULTS

Chip results showed that expression of all 18 DE genes were decreased in the cases compared to the controls (P < 0.05). Expression of ESR1 were verified to be significantly decreased (P < 0.05).

CONCLUSION

Our results provided clues with the association among down-regulated expression of autophagy regulating and associated genes and low sperm quality. These findings revealed possible role of impaired autophagy in the mechanism of low sperm quality. Moreover, these may also provide potential targets for the treatment of low sperm quality.

Contextualizing Autophagy during Gametogenesis and Preimplantation Embryonic Development

Mammals face environmental stressors throughout their lifespan, which may jeopardize cellular homeostasis. Hence, these organisms have acquired mechanisms to cope with stressors by sensing, repairing the damage, and reallocating resources to increase the odds of long-term survival. Autophagy is a pro-survival lysosome-mediated cytoplasm degradation pathway for organelle and macromolecule recycling. Furthermore, autophagy efflux increases, and this pathway becomes idiosyncratic depending upon developmental and environmental contexts. Mammalian germ cells and preimplantation embryos are attractive models for dissecting autophagy due to their metastable phenotypes during differentiation and exposure to varying environmental cues. The aim of this review is to explore autophagy during mammalian gametogenesis, fertilization and preimplantation embryonic development by contemplating its physiological role during development, under key stressors, and within the scope of assisted reproduction technologies.

Influence of Non-conventional Sperm Quality Parameters on Field Fertility in Ovine

The prediction of the fertilizing ability of a seminal dose continues to be a primary aim in the field of artificial insemination (AI). To achieve this goal, in this study we have included the evaluation of some non-conventional sperm quality markers. A total of 3,906 ewes from 52 different farms were inseminated with 357 refrigerated seminal doses obtained from 45 mature Rasa Aragonesa rams. The same samples were used for sperm quality analysis including membrane integrity, capacitation status, oxygen consumption and apoptotic-like markers such as phosphatidylserine translocation (PS), plasmalemma disorganization/mitochondrial membrane potential, caspase activation and DNA damage. Seminal doses from the breeding (B) season presented higher percentages of intact membrane (IM), non permeant (NP) membrane with high mitochondrial membrane potential (ΔΨm) and IM without PS translocation spermatozoa than those from the non-breeding (NB) season. Therefore, we can conclude that there were less spermatozoa showing apoptotic-like features in the seminal doses from the B than the NB season, although these differences did not affect field fertility. Only the percentage of intact membrane, non-capacitated (IM-NC) spermatozoa showed a significant correlation with in vivo fertility (P = 0.005) and fecundity (P = 0.007) values obtained after cervical AI when all data were evaluated. When the data were sorted by season and distance to the farms where AI was performed, the correlation between the percentage of IM-NC spermatozoa and reproductive parameters increased in the NB season and progressively with remoteness from the farms. Some other sperm parameters, like NP with high ΔΨm, IM sperm without active caspases and DNA-intact spermatozoa, also showed significant correlations with the reproductive parameters in the sorted data. Moreover, the increment in both the percentage of IM-NC and DNA-intact spermatozoa would increase the probability of obtaining a fertility higher than the mean (>52%), as revealed by a multiple logistic regression analysis. In conclusion, we have identified two seminal markers—the percentage of intact membrane, non-capacitated spermatozoa, and DNA intact spermatozoa—which could be used as a test to discard males in AI programs, which is highly important from an economic point of view and can contribute to achieving satisfactory fertility rates.

Arthropod toxins inhibiting Ca2+ and Na+ channels prevent AC-1001 H3 peptide-induced apoptosis

Peptide toxins of arthropods are one of the potential sources of bioactive substances. Toxins are able to bind to calcium channels and block them. Ca²⁺ ions play an important role in many cell processes, in particular, in apoptosis. In this work, we study the effect of some arthropod toxins on intracellular processes associated with the induction of apoptosis. Synthetic analogs of U₅ -scytotoxin-Sth1a, ω-hexatoxin-Hv1a, ω-theraphotoxin-Hhn2a, and μ-agatoxin-Aa1a toxins-inhibitors of calcium L, P, and Q channels and sodium channels were used in the study. Apoptosis was induced by AC-1001 H3 peptide. We study the effect of toxins on the level of apoptosis, ROS, mitochondrial potential, GSH, and ATP in CHO-K1 cells. We show that all the tested toxins are able to dose dependently block the induction of apoptosis triggered by AC-1001 H3 and reduce the level of natural apoptosis in CHO-K1 cells. Cell incubation with apoptosis inducer AC-1001 H3 in the presence and absence of toxins causes an increase in the intracellular concentrations of ROS, ATP, and mitochondrial potential and decreases the GSH concentration. The present study reveals the antiapoptotic effect of a number of arthropod peptide toxins. The toxins studied can represent a novel approach used in the treatment of pathologies associated with the activation of apoptotic mechanisms.

Seminal plasma AnnexinA2 protein is a relevant biomarker for stallions which require removal of seminal plasma for sperm survival upon refrigeration†

Some stallions yield ejaculates that do not tolerate conservation by refrigeration prior to artificial insemination (AI), showing improvement after removal of most of the seminal plasma (SP) by centrifugation. In this study, the SP-proteome of 10 different stallions was defined through high-performance liquid chromatography with tandem mass spectrometry and bioinformatic analysis in relation to the ability of the ejaculates to maintain semen quality when cooled and stored at 5°C. Stallions were classified into three groups, depending on this ability: those maintaining good quality after direct extension in a commercial extender (good), stallions requiring removal of seminal plasma (RSP) to maintain seminal quality (good-RSP), and stallions, unable to maintain good semen quality even after RSP (poor). Pathway enrichment analysis of the proteins identified in whole equine SP using human orthologs was performed using g: profiler showing enriched Reactome and the Kyoto Encyclopedia of Genes and Genomes pathways related to hexose metabolism, vesicle mediated transport, post translational modification of proteins and immune response. Specific proteins overrepresented in stallions tolerating conservation by refrigeration included a peroxiredoxin-6 like protein, and transcobalamin-2, a primary vitamin B12-binding, and transport protein. Also, the protein involved in protein glycosylation, ST3 beta-galactoside alpha-2,3-sialyltransferase 1 was present in good stallions. These proteins were nearly absent in poor stallions. Particularly, annexinA2 appeared as to be the most powerful discriminant variable for identification of stallions needing RSP prior to refrigeration, with a P = 0.002 and a q value = 0.005. Overall this is the first detailed study of the equine SP-proteome, showing the potential value of specific proteins as discriminant bio-markers for clinical classification of stallions for AI.

Effects of glucose concentration in semen extender and storage temperature on stallion sperm quality following long-term cooled storage

In Experiment 1, the effects of glucose concentration in extender (0 mM, 67 mM, 147 mM, 270 mM; G0, G67, G147, and G270, respectively) and storage temperature of extended semen (5, 10, 15 and 20 °C) were evaluated after storage for up to 5 days (T0h to T120h). For all time points tested, mean total (TMOT) and progressive (PMOT) sperm motility were lower in G0 than all other treatment groups (P < 0.05). Mean curvilinear velocity (VCL) was lower in G0 than other treatment groups at all time points tested except T0h (P < 0.05). Mean percentage of plasma membrane/acrosome intact sperm (VAI) was similar among treatments at T0h, T72h, and T120h (P > 0.05). Mean TMOT and PMOT, were lower for semen stored at 20 °C than all lower storage temperatures (P < 0.05) at all time points. In Experiment 2, semen was stored at 10 °C in extender containing no added glucose (G0) or 147 mM glucose (G147). Following storage, semen was centrifuged and resuspended in extender containing no added glucose (G0 - G0 or G147 - G0, respectively) or 147 mM of glucose (G0 - G147 or G147 - G147, respectively). Mean TMOT, PMOT, and VCL were higher in G147 than G0 at all time periods tested (P < 0.05), whereas mean VAI was similar between these treatment groups throughout the experiment (P > 0.05). Mean TMOT and PMOT were higher in G0 - G147 than G0 - G0 at T72h and T120h (P < 0.05) and mean VCL was higher in G0 - G147 than G0 - G0 for all time periods. Mean TMOT, PMOT, and VCL were higher in G147 - G147 than G147 - G0 at all time points tested (P < 0.05), whereas mean VAI was similar between these two treatment groups for each of the time points (P > 0.05). In Experiment 3, the minimum concentration of glucose required to maintain sperm quality following long-term cooled storage (T120 h) was evaluated (G0, G5, G10, G20, G40, G67, G147 mM). At T120 h, mean TMOT was lowest in G0, G5, G10, and G20 (P < 0.05), whereas mean PMOT and VCL were lower in G0, G5, G10, and G20 than in G40, G67, and G147 (P < 0.05). Mean VAI was higher in G10 than G67, but similar among G10 and other treatment groups (P > 0.05). In conclusion, the absence of added glucose in extender reduced the motion characteristics of stallion sperm during long-term storage (5 days), but VAI was not affected. The use of temperatures between 5 and 15 °C for long-term storage (5 days) best maintained sperm motility and VAI. The threshold concentration of added glucose in extender required to optimize sperm motion characteristics was 40 mM.

Autophagy related gene expression status in patients diagnosed with azoospermia: A cross-sectional study

BACKGROUND

Autophagy affects various aspects of the male reproductive system. Any defects in this process may lead to azoospermia. However, the exact molecular mechanisms of the autophagy pathway have remained largely obscure. Therefore, the present study aimed to investigate levels of autophagy pathway gene expression (i.e. Lc3B, Beclin1, ATG5 and Bcl2) in azoospermic patients.

METHODS

The levels of Lc3B, Beclin1, ATG5 and Bcl2 mRNA expression in azoospermic patients and fertile males were evaluated by a real-time polymerase chain reaction technique. In addition, diagnostic evaluation based on the receiver-operating characteristic (ROC) curve was performed.

RESULTS

The results obtained showed the decreased expression of Lc3B, Beclin1 and ATG5 genes in infertile patients compared to the control group (p < 0.05), whereas Bcl2 expression was increased in samples (p < 0.05). A diagnostic evaluation by ROC curve and calculation of the area under the curve showed that, using a cut-off relative quantification of 4.550, 0.052, 0.056 and 0.012, the sensitivity of Lc3B, Beclin1, ATG5 and Bcl2 genes was 87.5%, 93.8%, 93.8% and 90%, respectively. In addition, a specificity of 76.7%, 76.7%, 93.3% and 81.2%, respectively, was observed.

CONCLUSIONS

As a first study, the current research suggests that an alteration in the expression of autophagy pathway genes may be associated with male infertility. Based on our finding, the increased expression of Bcl2 and formation of Becline1/Bcl2 complex, which inhibits Beclin1 recruitment, may lead to a decrease of the autophagy process in azoospermic patients. Accordingly, upon further investigation, the autophagy could be considered as an important aspect during spermatogenesis.

Autophagie et spermatozoïde

La spermiogenèse, étape ultime de la spermatogenèse, est un processus qui fait intervenir des acteurs qui participe à l’autophagie. C’est en effet lors de cette étape que se forme l’acrosome par fusion vésiculaire et que disparaît la majeure partie du cytoplasme du spermatozoïde. L’autophagie (littéralement « se manger soi-même »), en permettant l’élimination et le remplacement continuel des protéines et des organites non fonctionnels, assure le recyclage des constituants de la cellule. C’est un mécanisme cellulaire très conservé au sein des cellules eucaryotes. La machinerie de l’autophagie est également présente dans les spermatozoïdes. Elle régule la vitalité de ces cellules et leur mobilité. Les conséquences environnementales et comportementales sur l’autophagie et sur la spermatogenèse commencent à être étudiées. Le but de cette revue est de synthétiser les connaissances actuelles concernant les processus d’autophagie dans le gamète mâle mature.

Bioinformatic identification of key genes and molecular pathways in the spermatogenic process of cryptorchidism

This study aims to determine key genes and pathways that could play important roles in the spermatogenic process of patients with cryptorchidism. The gene expression profile data of GSE25518 was obtained from the Gene Expression Omnibus (GEO) database. Microarray data were analyzed using BRB-Array Tools to identify differentially expressed genes (DEGs) between high azoospermia risk (HAZR) patients and controls. In addition, other analytical methods were deployed, including hierarchical clustering analysis, class comparison between patients with HAZR and the normal control group, gene ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis, and the construction of a protein–protein interaction (PPI) network. In total, 1015 upregulated genes and 1650 downregulated genes were identified. GO and KEGG analysis revealed enrichment in terms of changes in the endoplasmic reticulum cellular component and the endoplasmic reticulum protein synthetic process in the HAZR group. Furthermore, the arachidonic acid pathway and mTOR pathway were also identified as important pathways, while RICTOR and GPX8 were indentified as key genes involved in the spermatogenic process of patients with cryptorchidism. In present study, we found that changes in the synthesis of endoplasmic reticulum proteins, arachidonic acid and the mTOR pathway are important in the incidence and spermatogenic process of cryptorchidism. GPX8 and RICTOR were also identified as key genes associated with cryptorchidism. Collectively, these data may provide novel clues with which to explore the precise etiology and mechanism underlying cryptorchidism and cryptorchidism-induced human infertility.

Redox Regulation and Oxidative Stress: The Particular Case of the Stallion Spermatozoa

Redox regulation and oxidative stress have become areas of major interest in spermatology. Alteration of redox homeostasis is recognized as a significant cause of male factor infertility and is behind the damage that spermatozoa experience after freezing and thawing or conservation in a liquid state. While for a long time, oxidative stress was just considered an overproduction of reactive oxygen species, nowadays it is considered as a consequence of redox deregulation. Many essential aspects of spermatozoa functionality are redox regulated, with reversible oxidation of thiols in cysteine residues of key proteins acting as an “on–off” switch controlling sperm function. However, if deregulation occurs, these residues may experience irreversible oxidation and oxidative stress, leading to malfunction and ultimately death of the spermatozoa. Stallion spermatozoa are “professional producers” of reactive oxygen species due to their intense mitochondrial activity, and thus sophisticated systems to control redox homeostasis are also characteristic of the spermatozoa in the horse. As a result, and combined with the fact that embryos can easily be collected in this species, horses are a good model for the study of redox biology in the spermatozoa and its impact on the embryo.

Combined addition of superoxide dismutase, catalase and glutathione peroxidase improves quality of cooled stored stallion semen

During cold storage stallion spermatozoa experience undergo oxidative stress, which can impair sperm function and fertilizing capacity. Superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPX) are the main endogenous enzymatic antioxidants in stallion seminal plasma, and counteract reactive oxygen species. Semen dilution reduces the endogenous antioxidant concentrations. The aim of this study was to investigate whether addition of 15 IU/mL each of SOD, CAT, and GPX to diluted stallion semen would ameliorate a reactive oxygen-mediated decrease in semen quality during 72 h of storage at 5 °C. Ejaculates (n = 7) were divided in two aliquots and diluted in INRA 96 without (control) or with addition of antioxidants. Semen analysis was performed at the time of dilution and every 24 h during chilled storage. Antioxidant supplementation completely inhibited the storage-dependent increase in activated caspase 3 (P < 0.05). Concomitantly, the antioxidant-supplemented samples had a greater percentage of viable, motile and rapidly moving sperm than control samples after 72 h storage (P < 0.05). The DNA damage, as evaluated by TUNEL assay and SCSA, increased with storage time (P < 0.05). Antioxidant supplementation did not prevent, but did significantly reduce the increase in DNA strand breakage. The results indicate part of the intrinsic apoptotic pathway leading to effector caspase activation was inhibited, although an activation of molecules with endonuclease activity still occurred. In conclusion, adding equal concentrations of SOD, CAT and GPX to a semen extender suppressed caspase-3 activation and improved preservation of stallion sperm motility and viability during 72 h of storage at 5 °C.

Advances in Cryopreservation of Bull Sperm

Cryopreservation of semen and artificial insemination have an important, positive impact on cattle production, and product quality. Through the use of cryopreserved semen and artificial insemination, sperm from the best breeding bulls can be used to inseminate thousands of cows around the world. Although cryopreservation of bull sperm has advanced beyond that of other species, there are still major gaps in the knowledge and technology bases. Post-thaw viability of sperm is still low and differs significantly among the breeding bulls. These weaknesses are important because they are preventing advances both in fundamental science of mammalian gametes and reproductive biotechnology. Various extenders have been developed and supplemented with chemicals to reduce cryodamage or oxidative stress with varying levels of success. More detailed insights on sperm morphology and function have been uncovered through application of advanced tools in modern molecular and cell biology. This article provides a concise review of progress in the cryopreservation of bull sperm, advances in extender development, and frontiers using diverse techniques of the study of sperm viability. This scientific resource is important in animal biotechnology because with the advances in discovery of sperm fertility markers, there is an urgent need to improve post-thaw viability and fertility of sperm through enhanced cryopreservation for precision agriculture to produce food animals to ensure food security on the global scale.

Advances in understanding mechanisms of long-term sperm storage-the soft-shelled turtle model

Long-term sperm storage is a special reproductive strategy, which can extend the time window between mating and fertilization in some animal species. Spermatozoa of the soft-shelled turtle, Pelodiscus sinensis, can be stored in the epididymis and oviduct for at least six months and one year, respectively. How spermatozoa can be stored in vivo for such a prolonged period is yet to be explained. We analyze the mechanisms that contribute to long-term sperm storage in P. sinensis, and compare them with other species from three different perspectives: the spermatozoon itself, the storage microenvironment and the interaction between the spermatozoon and microenvironment. Characteristics of soft-shelled turtle spermatozoa itself, such as the huge cytoplasmic droplet with its content of several large lipid droplets (LDs) and onion-like mitochondira, facilitate long-term sperm storage. The microenvironment of reproductive tract, involving in the secretions, structural barriers, exosomes, androgen receptors, Toll-like receptors and survival factor Bcl-2, are important for the maintenance of spermatozoa long-term storage. Sperm heads are always embedded among the oviductal cilia and even intercalate into the apical hollowness of the ciliated cells, indicating that the ciliated cells support the stored spermatozoa. RNA seq is firstly used to detect the molecular mechanism of sperm storage, which shows that autophagy, apoptosis and immune take part in the long-term sperm storage in this species.

Sperm handling in aquatic animals for artificial reproduction

Artificial reproduction involves collection and handling of gametes in a way that secures their quality and maximizes the fertilization outcome. In addition to initial sperm quality, numerous steps can affect the final result of fertilization, from the sperm collection process until gamete mixing (or co-incubation) when the spermatozoon enters or fuses with the oocyte. In this review, we summarize the whole process of sperm handling, from collection until fertilization for fish, penaeid shrimp, bivalve mollusks and marine mammals. To obtain sperm from captive animals, techniques vary widely across taxa, and include stripping by abdominal massage or testis surgical removal in fish, spermatophore collection in penaeid shrimps, gonadal scarification or temperature shock in bivalve mollusks, and voluntary collection via positive reinforcement in mammals. In most cases, special care is needed to avoid contamination by mucus, seawater, urine, or feces that can either activate sperm motility and/or decrease its quality. We also review techniques and extender solutions used for refrigerated storage of sperm across the aforementioned taxa. Finally, we give an overview of the different protocols for in vivo and in vitro fertilization including activation of sperm motility and methods for gamete co-incubation. The present study provides valuable information regarding breeder management either for animal production or species conservation.

Apoptotic-like changes in epididymal spermatozoa of soft-shelled turtles, Pelodiscus sinensis, during long-term storage at 4 ºC

Apoptosis is a physiological phenomenon that has been recognized as a cause of sperm death during cryopreservation in endothermic mammals. There is, however, no data on its role in sperm death during cooled storage in ectothermic animals. In this study, spermatozoa from the epididymis of soft-shelled turtle were investigated to identify the mechanism of spermatozoa apoptotic-like changes during storage at 4 °C. In this study, there was survival of spermatozoa for more than 40 Days when stored at 4 °C. During cooled storage, sperm kinematics was evaluated using CASA system. Values for all sperm motility variables decreased during the period of storage; while for velocity curvilinear (VCL) there was a further decrease after 20 Days of storage. Results from flow cytometry analysis indicated that there was a significant increase in the percentage of apoptotic spermatozoa, but there was no change in the percentage of necrosis. Furthermore, the concentration of cellular ROS increased after 20 Days of storage at 4 °C. The results using JC-1 staining indicated there was a decrease in MMP of spermatozoa as the duration of storage at 4 °C increased. Nuclear fragmentation of spermatozoa was observed using TEM on Day 30 of storage. There were large amounts of pro-apoptotic cytochrome c (Cytc) and cleaved caspase-9/3 proteins detected using western blot analysis after 30 days of spermatozoa storage at 4 °C. These findings indicate ROS generation induces mitochondria damage after 20 days of storage at 4 °C, which can induce spermatozoa apoptotic-like changes during storage of soft-shelled turtle spermatozoa.

Baicalin protects mouse testis from injury induced by heat stress

Heat stress has been documented to reduce reproductive performance of female animals through injury to germ cells, with few studies available in male animals. The objectives of this study were to evaluate protective effects of baicalin on testicular tissue damage of mice subjected to heat stress and its related mechanisms. In this experiment, A total of forty mice were divided into four groups, including control group (C), baicalin group (B), heat stressed group (H) and heat stress with baicalin treatment (H + B) group. Morphological changes, activities of antioxidant enzymes and apoptosis-related parameters in the mice testes tissue were monitored. The results showed that the process of spermatogenesis in mice testis was impaired and the cellular apoptosis increased due to acute heat stress at 41 °C. Interestingly, the tissue damage was alleviated with the significant (P < 0.05) increase in the activities of SOD, CAT and GSH-Px enzymes, decrease (P < 0.05) in MDA content and number of cellular apoptosis recorded in mice of H + B group compared with those in mice from H group. In addition, the Fas, FasL and P-JNK protein expressions were significantly (P < 0.05) increased; and apaf-1, caspase-3, -9 were slightly expressed in the H group, while there was no difference in Bcl-2 expression, compared with C, B and H + B groups. The above results clearly indicate that heat stress induces macroscopic/apoptotic and oxidative changes in the testicular tissue of mice; these changes are alleviated by Baicalin through increasing anti-oxidative enzyme activities and possibly through blocking Fas/FasL pathway.

The impact of autophagy in spermiogenesis

Autophagy is an evolutionarily conserved self-digestion process which is essential to keep basal homeostasis in a cell. During this process, degradation and recycling of many cytoplasmic components including the long-lived, unnecessary or aggregated proteins and damaged organelles is achieved through lysosomal machinery. Autophagy has a critical role for lower eukaryotic organisms such as yeast to survive and adapt to nutrient starvation conditions. In addition to this primary function, autophagy appears as a crucial mechanism for cell differentiation and development enabling the cells to modify their content and morphology in response to environmental and hormonal cues. A recent study by Shang et al.1 shed more light on the molecular mechanisms of how autophagy regulates spermiogenesis.

Comparison of main molecular markers involved in autophagy and apoptosis pathways between spermatozoa of infertile men with varicocele and fertile individuals

Abnormal dilatation and tortuosity of the pampiniform plexus within the spermatic cord are termed varicocele which leads to impaired spermatogenesis due to heat-related oxidative stress and cell death. Previously, it was shown that both apoptosis and autophagy pathways were activated by heat in germ cells of mouse in vivo and in vitro. But, status of these pathways is not clear in chronic state of heat stress such as varicocele. Therefore, we aimed to access sperm apoptotic markers (active caspases 3/7 and DNA fragmentation), and autophagic markers (Atg7 and LC3 proteins) as primary outcomes, and also sperm parameters and protamine deficiency as secondary outcomes between 23 infertile men with varicocele and 16 fertile individuals. Sperm parameters were assessed according to World Health Organization 2010 protocol. Apoptotic markers (active caspases 3/7 and DNA fragmentation), autophagic markers (Atg7 and LC3 proteins), and protamine deficiency were evaluated by flow cytometry, fluorescence microscope, and western blotting techniques. Mean of autophagy and apoptosis markers, and also protamine deficiency have significantly increased in infertile men with varicocele compared to fertile individuals, but autophagy and apoptosis markers did not significantly correlate with each other. In conclusion, it seems that both apoptosis and autophagy pathways are independently active in spermatozoa of infertile men with varicocele.

The physiological roles of autophagy in the mammalian life cycle

Autophagy is primarily an efficient intracellular catabolic pathway used for degradation of abnormal cellular protein aggregates and damaged organelles. Although autophagy was initially proposed to be a cellular stress responder, increasing evidence suggests that it carries out normal physiological roles in multiple biological processes. To date, autophagy has been identified in most organs and at many different developmental stages, indicating that it is not only essential for cellular homeostasis and renovation, but is also important for organ development. Herein, we summarize our current understanding of the functions of autophagy (which here refers to macroautophagy) in the mammalian life cycle.

Sodium-dependent organic anion transporter (Slc10a6-/-) knockout mice show normal spermatogenesis and reproduction, but elevated serum levels for cholesterol sulfate

The sodium-dependent organic anion transporter SOAT (gene name SLC10A6 in man and Slc10a6 in mice) is a plasma membrane transporter for sulfated steroids, which is highly expressed in germ cells of the testis. SOAT can transport biologically inactive sulfated steroids into specific target cells, where they can be reactivated by the steroid sulfatase (STS) to biologically active, unconjugated steroids known to regulate spermatogenesis. Significantly reduced SOAT mRNA expression was previously found in different forms of impaired spermatogenesis in man. It was supposed that SOAT plays a role for the local supply of steroids in the testis and consequently for spermatogenesis and fertility. Thus, an Slc10a6^-/- Soat knockout mouse model was established by recombination-based target deletion of the Slc10a6 gene to elucidate the role of Soat in reproduction. However, the Slc10a6^-/- knockout mice were fertile, produced normal litter sizes, and had normal spermatogenesis and sperm vitality. This phenotype suggests that the loss of Soat can be compensated in the knockout mice or that Soat function is not essential for reproduction. In addition to reproductive phenotyping, a comprehensive targeted steroid analysis including a set of 9 un-conjugated and 12 sulfo-conjugated steroids was performed in serum of Slc10a6^-/- knockout and Slc10a6^+/+ wildtype mice. Only cholesterol sulfate, corticosterone, and testosterone (only in the males) could be detected in considerable amounts. Interestingly, male Slc10a6^-/- knockout mice showed significantly higher serum levels for cholesterol sulfate compared to their wildtype controls. As cholesterol sulfate has a broader impact apart from the testis, further analysis of this phenotype will include other organs such as skin and lung, which also show high Soat expression in the mouse.

Diet-induced obesity impairs spermatogenesis: a potential role for autophagy

Autophagy is an evolutionarily conserved process that plays a crucial role in maintaining a series of cellular functions. It has been found that autophagy is closely involved in the physiological process of spermatogenesis and the regulation of sperm survival and motility. However, the role of autophagy in high-fat diet (HFD)-induced impaired spermatogenesis remains unknown. This study was designed to investigate the role of autophagy in HFD-induced spermatogenesis deficiency and employed chloroquine (CQ) to inhibit autophagy and rapamycin (RAP) to induce autophagy. 3-methyladenine (3-MA) and CQ were administered via intratesticular injection in vivo. The effects of CQ and 3-MA on the parameters of spermatozoa co-cultured with palmitic acid (PA) in vitro were also investigated. Human semen samples from obese, subfertile male patients were also collected to examine the level of autophagy. The results suggested that HFD mice subjected to CQ showed improved spermatogenesis. Inhibiting autophagy with CQ improved the decreased fertility of HFD male mice. Moreover, the in vivo and in vitro results indicated that both CQ and 3-MA could suppress the pathological changes in spermatozoa caused by HFD or PA treatment. Additionally, the excessive activation of autophagy was also observed in sperm samples from obese, subfertile male patients.

Computational flow cytometry reveals that cryopreservation induces spermptosis but subpopulations of spermatozoa may experience capacitation-like changes

The reduced lifespan of cryopreserved spermatozoa in the mare reproductive tract has been attributed to both capacitative and apoptotic changes. However, there is a lack of studies investigating both phenomena simultaneously. In order to improve our knowledge in this particular point, we studied in raw and frozen-thawed samples apoptotic and capacitative markers using a wide battery of test based in flow cytometry. Apoptotic markers evaluated were caspase 3 activity, externalization of phosphatidylserine (PS), and mitochondrial membrane potential. Markers of changes resembling capacitation were membrane fluidity, tyrosine phosphorylation, and intracellular sodium. Conventional and computational flow cytometry using nonlinear dimensionally reduction techniques (t-distributed stochastic neighbor embedding (t-SNE)) and automatic classification of cellular expression by nonlinear stochastic embedding (ACCENSE) were used. Most of the changes induced by cryopreservation were apoptotic, with increase in caspase 3 activation (P < 0.01), PS translocation to the outer membrane (P < 0.001), loss of mitochondrial membrane potential (P < 0.05), and increase in intracellular Na+ (P < 0.01). Average values of markers of capacitative changes were not affected by cryopreservation; however, the analysis of the phenotype of individual spermatozoa using computational flow cytometry revealed the presence of subpopulations of spermatozoa experiencing capacitative changes. For the first time advanced computational techniques were applied to the analysis of spermatozoa, and these techniques were able to disclose relevant information of the ejaculate that remained hidden using conventional flow cytometry.

Cooled-storage of equine semen does not induce major changes in sperm DNA methylation

A decrease in fertility of equine semen during cooled-storage so far has mainly been attributed to changes in sperm membrane function. In the present study we hypothesized that cooled-storage also changes the sperm DNA methylation level. For this purpose, semen was collected from 10 fertile stallions and processed for cooled-storage at 5 °C. Two final concentrations, 50 × 10⁶ and 100 × 10⁶ cells/mL, were used. Semen was analyzed for total motility, progressive motility, membrane integrity, phosphatidylserine translocation (PST), mitochondrial membrane potential and chromatin condensation, immediately after processing and at 24 h-intervals until 72 h of storage. DNA cytosine methylation was assessed by ELISA after DNA extraction and denaturation. DNA methylation did neither change over time nor was affected by semen concentration. Total motility, progressive motility, membrane integrity, PST, mitochondrial membrane potential and chromatin condensation changed over storage time, but no differences between semen concentrations could be demonstrated. The results demonstrate that cooled-storage of equine semen does not induce changes in sperm DNA cytosine methylation. In cooled-semen of good quality, a concentration of 100 × 10⁶ sperm/mL does not affect semen longevity. It can be concluded that a better fertility of cooled-stored than cryopreserved stallion semen is at least in part a result of only minor influences of cooled-storage on DNA integrity and methylation.

Autophagy-related proteins are functionally active in human spermatozoa and may be involved in the regulation of cell survival and motility

Macroautophagy (hereafter autophagy) is an evolutionarily highly conserved cellular process that participates in the maintenance of intracellular homeostasis through the degradation of most long-lived proteins and entire organelles. Autophagy participates in some reproductive events; however, there are not reports regarding the role of autophagy in the regulation of sperm physiology. Hence, the aim of this study was to investigate whether autophagy-related proteins are present and functionally active in human spermatozoa. Proteins related to autophagy/mitophagy process (LC3, Atg5, Atg16, Beclin 1, p62, m-TOR, AMPKα 1/2, and PINK1) were present in human spermatozoa. LC3 colocalized with p62 in the middle piece of the spermatozoa. Autophagy activation induced a significant increase in motility and a decrease in PINK1, TOM20 expression and caspase 3/7 activation. In contrast, autophagy inhibition resulted in decreased motility, viability, ATP and intracellular calcium concentration whereas PINK1, TOM20 expression, AMPK phosphorylation and caspase 3/7 activation were significantly increased. In conclusion our results show that autophagy related proteins and upstream regulators are present and functional in human spermatozoa. Modification of mitochondrial proteins expression after autophagy activation/inhibition may be indicating that a specialized form of autophagy named mitophagy may be regulating sperm function such as motility and viability and may be cooperating with apoptosis.

Global analysis of differential gene expression related to long-term sperm storage in oviduct of Chinese Soft-Shelled Turtle Pelodiscus sinensis

Important evolutionary and ecological consequences arise from the ability of female turtles to store viable spermatozoa for an extended period. Although previous morphological studies have observed the localization of spermatozoa in Pelodiscus sinensis oviduct, no systematic study on the identification of genes that are involved in long-term sperm storage has been performed. In this study, the oviduct of P. sinensis at different phases (reproductive and hibernation seasons) was prepared for RNA-Seq and gene expression profiling. In total, 2,662 differentially expressed genes (DEGs) including 1,224 up- and 1,438 down-regulated genes were identified from two cDNA libraries. Functional enrichment analysis indicated that many genes were predominantly involved in the immune response, apoptosis pathway and regulation of autophagy. RT-qPCR, ELISA, western blot and IHC analyses showed that the expression profiles of mRNA and protein in selected DEGs were in consistent with results from RNA-Seq analysis. Remarkably, TUNEL analysis revealed the reduced number of apoptotic cells during sperm storage. IHC and TEM analyses found that autophagy occurred in the oviduct epithelial cells, where the spermatozoa were closely attached. The outcomes of this study provide fundamental insights into the complex sperm storage regulatory process and facilitate elucidating the mechanism of sperm storage in P. sinensis.

New flow cytometry approaches in equine andrology

Flow cytometry is currently recognized as a robust tool for the evaluation of sperm quality and function. However, within equine reproduction, this technique has not reached the sophistication of other areas of biology and medicine. In recent years, more sophisticated flow cytometers have been introduced in andrology laboratories, and the number of tests that can be potentially used in the evaluation of sperm physiology has increased accordingly. In this review, recent advances in the evaluation of stallion spermatozoa will be discussed. These new techniques in flow cytometry are able to simultaneously measure damage to different sperm regions and/or changes in functionality.

The germline-enriched Ppp1r36 promotes autophagy

Spermatogenesis is a highly regulated process during which haploid sperm cells are generated. Although autophagy is involved in the spermatogenesis process, the molecular pathways and regulations of autophagy in germ cell development remain elusive. Here, we showed that Ppp1r36, a regulatory subunit of protein phosphatase 1, is expressed during gonadal development, mainly in testes during spermatogenesis. Autophagy protein LC3 (microtubule associated protein 1 light chain 3), especially its active form LC3-II, had a similar expression pattern to Ppp1r36. Moreover, LC3-II level and puncta analysis showed that autophagy is up-regulated around 21 dpp (day postpartum) in postnatal testis, indicating a potential role of autophagy during the first wave of spermatogenesis. We demonstrated that Ppp1r36 promotes autophagosome formation upon starvation induction. Further autophagy flux analysis using a tandem fluorescent indicator, mCherry-GFP-LC3, confirmed that Ppp1r36 participated in autophagy. We further determined that Ppp1r36 is associated with Atg16L1 (autophagy related 16-like 1) in autophagy of starvation induction. Thus, our results uncover a potential role of the regulatory subunit Ppp1r36 of protein phosphatase 1 in enhancing autophagy during spermatogenesis.

The autophagy-related protein LC3 is processed in stallion spermatozoa during short-and long-term storage and the related stressful conditions

Use of cooled and frozen semen is becoming increasingly prevalent in the equine industry. However, these procedures cause harmful effects in the sperm cell resulting in reduced cell lifespan and fertility rates. Apoptosis and necrosis-related events are increased during semen cryopreservation. However, a third type of cell death, named autophagy, has not been studied during equine semen storage. Light chain (LC)3 protein is a key component of the autophagy pathway. Under autophagy activation, LC3-I is lipidated and converted to LC3-II. The ratio of LC3-II/LC3-I is widely used as a marker of autophagy activation. The main objective of this study was to investigate whether LC3 is processed during cooling, freezing and the stressful conditions associated with these technologies. A secondary objective was to determine if LC3 processing can be modulated and if that may improve the quality of cryopreserved semen. LC3 processing was studied by Western blot with a specific antibody that recognized both LC3-I and LC3-II. Viability was assessed by flow cytometry. Modulation of LC3-I to LC3-II was studied with known autophagy activators (STF-62247 and rapamycin) or inhibitors (chloroquine and 3-MA) used in somatic cells. The results showed that conversion of LC3-I to LC3-II increased significantly during cooling at 4°C, freezing/thawing and each of the stressful conditions tested (UV radiation, oxidative stress, osmotic stress and changes in temperature). STF-62247 and rapamycin increased the LC3-II/LC3-I ratio and decreased the viability of equine sperm, whereas chloroquine and 3-MA inhibited LC3 processing and maintained the percentage of viable cells after 2 h of incubation at 37°C. Finally, refrigeration at 4°C for 96 h and freezing at -196°C in the presence of chloroquine and 3-MA resulted in higher percentages of viable cells. In conclusion, results showed that an 'autophagy-like' mechanism may be involved in the regulation of sperm viability during equine semen cryopreservation. Modulation of autophagy during these reproductive technologies may result in an improvement of semen quality and therefore in higher fertility rates.